1. Field of the Invention
This invention relates broadly to endoscopic instruments. More particularly, this invention relates to loop electrodes which are used in electrocautery probes with a resectoscope.
2. State of the Art
Electrosurgical resection is a procedure in which damaged or enlarged tissue is excised with an electrocautery probe. Transurethral resection is an electrosurgical procedure in which a portion of the prostrate is excised by means of an instrument passed through the urethra. Endometrial ablation is an electrosurgical alternative procedure to hysterectomy for women with menorrhagia (abnormal or excessive uterine bleeding). In both procedures, the instrument typically used is called a resectoscope or hysteroscope. Prior art FIG. 1 shows a typical resectoscope 10 with an electrocautery probe 12. The resectoscope 10 includes a distal guide tube 14 and a proximal handle 16. A telescope 18 is inserted through the guide tube 14 and is provided with a proximal eye piece 20 for viewing the interior of the bladder or other operative site. The cautery probe 12 has a distal electrode 22 which is mounted between a pair of arms 23, 25. The arms 23, 25 are joined at their proximal ends to an electrode lead 27 which is coupled via the handle 16 to a wire 24 which is coupled to a source of cautery current (not shown). A mounting sleeve 29 is provided on the probe 12 for slideably coupling it to the guide tube 14. The mounting sleeve 29 is typically located at the point where the arms 23, 25 are joined to the electrode lead 27. The handle 16 is generally capable of axially sliding the probe 12 and its distally mounted electrode 22 relative to the guide tube 14.
The resection procedure involves applying a cauterizing voltage to the electrode 22 and moving the electrode slowly through or over the prostate or endometrium while viewing the tissue through the scope 18. Thermal energy is applied through the electrode to the prostate or the endometrium so that tissue is excised. The resectoscope and cautery probe are also useful in other procedures for resecting the uterus, ureter, or renal pelvis.
Known electrodes for use in resectoscopes are available in many different shapes and sizes. U.S. Pat. No. 4,917,082 to Grossi et al., for example, discloses several embodiments of a "Resectoscope Electrode" including a coagulating electrode, a knife electrode, a puncrate electrode, and a roller electrode, among others. Electrodes for use with resectoscopes are also widely available from Olsen Electrosurgical, Inc., Concord, Calif. They are available as blades, needles, balls, loops, spear tips, flexible wires, semi-circular wires, hooks, spatulas and blunt tips.
The loop electrode 22, which is shown in FIGS. 1 and 2 is the presently preferred type of electrode for prostatic resection because it can be used to cut and to coagulate. The disadvantage of the loop electrode is that in order to make the electrode sharp enough to cut, it must be made relatively thin with little surface area. The small surface area of the loop electrode compromises its effectiveness as a coagulating tool. Thus, in a prostatic resection procedure, 80% of the time devoted to the procedure is used to coagulate the prostate and stop it from bleeding.